The present invention relates generally to a disposable diaper and particularly to a disposable diaper improved so as to protect the wearer against soil with feces.
One example of the disposable diaper is disclosed in Published Japanese Translation of PCT International Publication for Patent Application No. 1997-506528 (Reference 1). In this known diaper, a topsheet laid so as to come close to the wearer's skin and formed with an opening defined by a pair of opposite side edges extending in parallel to each other and these side edges are provided with elastic members which are gradually spaced from each other as these elastic members extend from an anterior portion toward a posterior portion of the opening. In the known diaper, the elastic members extending in this manner function to space the opposite side edges from each other and thereby to assure that the diaper put on the wearer can maintain a predetermined width of the opening.
Another example of the disposable diaper is also disclosed in Japanese Unexamined Patent Application Publication No. 2002-11044 (Reference 2). This diaper is particularly provided above the topsheet with a skin-contact sheet serving to protect the wearer's hip from soil with feces. The skin-contact sheet has longitudinally opposite ends bonded to the topsheet or the backsheet and is formed in its crotch region with an opening surrounded by an elastic member bonded in its stretched state to the skin-contact sheet. This diaper is put on the wearer's body with the opening overlapping the wearer's anus.
In the diaper disclosed in Reference 1, the topsheet has its front edge as well as its rear edge fixed to the diaper chassis and inevitably comes in direct contact with the buttocks and the external genital of the wearer. Such topsheet is necessarily hydrophilic and liquid-pervious since the topsheet must allow urine to permeate this topsheet. The topsheet wet with urine continuously in contact with the wearer's skin may cause diaper rash. In addition, if such liquid-pervious topsheet is loaded with the wearer's body weight as the wearer sits down or lies down, it is likely that feces staying below the topsheet may flow backs and soil the wearer's external genital and the vicinity thereof. Furthermore, in the diaper disclosed in Reference 1, the opening is formed at a long distance from the regions in which the topsheet is fixed. Consequentially, it is required to keep the elastic members in tight contact with the wearer's skin and thereby to alleviate deformation of the opening in view of the fact that the opening is formed in the crotch region which is apt to be deformed as the legs of the wearer move. However, the elastic members continuously kept in contact with the wearer's skin too tightly may cause diaper eczema. The elastic members gradually spaced from each other as these elastic members extend from an anterior portion toward a posterior portion of the opening may preferably assume that the opening also presents the corresponding shape. An appropriate transverse dimension of the opening in the vicinity of the anus is usually in a range of 3 to 6 cm to receive feces. However, the transverse dimension of the opening shaped so as to be gradually enlarged as it gets nearer to the rear end of the diaper may exceeds such appropriate range and make it difficult to protect the wearer's skin from soil with feces.
In the diaper disclosed in Reference 2, the elastic member is provided so as to surround the opening and thereby the skin-contactable sheet can be kept in close contact with the wearer's skin in front of the opening as well as behind the opening. However, similarly to the diaper disclosed in Reference 1, the skin-contactable sheet is bonded to the topsheet or the backsheet at the longitudinally opposite ends of the diaper and consequentially the crotch region of the diaper is repetitively compressed and decompressed depending on movement of the wearer's legs. In response to such repeated compression and decompression, the opening is repetitively deformed until the opening is out of alignment with the anus and feces is not received by the opening but soils the wearer's skin. Furthermore, the skin-contactable sheet is bonded to elastic members of front and rear waist regions laid along the longitudinally opposite ends of the diaper, respectively, and the opening may be deformed as a stretch ratio changes depending on the individual wearer's waist dimension.